1. Field of the Invention
The present invention relates to a finder and, in particular, to a finder of a camera equipped with a zooming function.
2. Related Background Art
A camera which can switch between wide-angle and telephoto photographing modes is typically equipped with a zoom finder which changes the magnification of its field of view in response to switching between these modes. FIG. 5 is a schematic view showing a configuration of such a conventional finder. This finder A is configured such that movable lenses E and F are disposed on an optical axis D between an objective lens B and an eyepiece C, and a coil spring G is disposed between the movable lenses E and F so as to urge them toward each other, whereby the movable lenses E and F are moved by a cam mechanism or the like. As the photographing mode is switched between wide angle and telephoto, the movable lenses E and F move appropriately, thus changing the range of field of view of the finder A in conformity to the photographing range.
In the above-mentioned finder A, it is important for the movable lenses E and F to accurately move along the optical axis D when switching from wide angle to telephoto or vice versa. For example, when the movable lenses E and F fluctuate, the object image viewed through the finder A shifts during switching between wide angle and telephoto. When a high-quality lens is used in this case, the fluctuation (hereinafter referred to as "image blur") of the object image or the like is enhanced as the object image becomes more vivid, whereby the intrinsic performances of the lens may not fully be exhibited.
As means against such fluctuation of the movable lenses E and F, it has been proposed to attach the coil spring G to the movable lenses E and F as being twisted. For example, the coil spring G is attached to the movable lenses E and F in a state where one end side of the coil spring G is fixed while the other end side is twisted several times, thus applying an urging force to the movable lenses E and F not only in a tensile direction in parallel with the optical axis but also in a direction orthogonal to the optical axis, whereby a part of the movable lenses E and F abuts a frame or the like so as to be prevented from fluctuating.
With this means in which the coil spring G is twisted, in order to make a camera, there is consequently needed a step of attaching the coil spring G to the movable lenses E and F while twisting it. Such a step is quite difficult and inevitably lowers the efficiency in manufacture. Also, a part of the movable lenses E and F is forcibly rubbed against the frame or the like every time they move, thus additionally requiring means against friction so as to enable them to be used for a long time.